I sent an email of complaint to Virgin Media via http://www.ispa.org.uk
and they telephoned me within 30 minutes and dealt with my complaint.
Long story cut short..I had a contract with Virgin, rolling contract and I agreed to enter into a 12 month contract as long as they would charge me £10. They agreed. They then (after 3 months) start charging me £18.
Use this link below if you are in a disagreement with your ISP.